Well, if you think about it, the case for Ridley's playability is pretty strong when you look at certain facts.
For one, there's no reason to resize Ridley down to less than half of his brawl size (other than to balance him for playability); especially if Sakurai wants everyone to believe that Ridley is going to reprise a similar role to the last game (boss status). Also, the gimpy frame skipping shadow couldn't possibly reflect a pre-scripted boss animation. Just these things are enough to just about see through Sakurai's ruse, but then you also have the fact that he is STILL hiding Ridley from even so much as a screen shot or further mention after he talked so much about Yellow Devil and even Dark Emperor. Hell, compared to this time, Sakurai mentioned Ridley WAAAY more during the days leading up to brawl with the music and pictures/sse hype etc. It doesn't make sense to reduce that attention to Ridley when his popularity has only grown since brawl. I'll even bet he is counting on the fact that people are already figuring it out just so he can bring down the house at E3. It honestly would be a show-stealer.
I think people should put their worries aside and take a long hard look at the facts. I understand that it's a safe move to keep your expectations relatively low in the unlikely event that Sakurai says Ridley is indeed a boss/hazard, but for me personally, for him to disconfirm Ridley after all this time, and after the way (or lack thereof) that he presented Ridley, it would be just as shocking for me to hear that as it would be if Sakurai suddenly revealed Yellow Devil to be playable.
Bottom line is that I think us fans should rest assured based on the facts given and figured out so far. The reason there is so much speculation on this is because Sakurai purposely left a lot of room to speculate. And as others have said, it's a fantastic way to maximize the hype for show time.